1. Field of the Invention
The present invention relates to pressure transmitter devices and pressure transmission methods and particularly to a pressure transmitter device which can be used in nuclear power plants, petroleum refining plants, chemical plants and the like in a preferable manner for measuring a pressure of a fluid or a pressure difference between two points and transmitting a detection signal thereof.
2. Description of the Related Art
Pressure transmitter devices transfer a pressure of a measuring fluid received by a diaphragm to a sensor by a fill fluid filling in a hydraulic path and externally transmits an electrical signal detected by the sensor. The pressure transmitter devices include pressure transmitters for measuring an absolute pressure and differential pressure transmitters for measuring a differential pressure. These pressure transmitter devices are used in nuclear power plants, petroleum refining plants, and the like and thus required of an accuracy of, for example, +/−1% in order to secure safety in the plant or to ensure product quality. However, it has been difficult to maintain the accuracy for a long term due to influence by hydrogen permeated from the outside of the pressure transmitter device.
For example, a part of hydrogen (hydrogen molecule, hydrogen atom, and hydrogen radical) contained in a measuring fluid permeates through the diaphragm. Thereafter, the permeated hydrogen accumulates in the fill fluid filling the hydraulic path in the form of bubbles. Moreover, the fill fluid decomposes due to radiation or heat, thereby generating a hydrogen radical or a hydrocarbon radical such as a methyl radical. Furthermore, these radicals are bonded with each other and thereby generate hydrogen molecules or hydrocarbon such as methane. Similarly to the aforementioned hydrogen that permeates through the diaphragm, the above also accumulates inside the hydraulic path. In this manner, when hydrogen bubbles or hydrocarbon bubbles accumulate inside the hydraulic path, a pressure inside the hydraulic path increases and a variation in the pressure applied to the diaphragm is not correctly transferred to the sensor. This results in a decreased measurement accuracy.
Meanwhile, a technique disclosed in JP-2014-089171-A is known to suppress accumulation of hydrogen bubbles or hydrocarbon bubbles inside a hydraulic path. JP-2014-089171-A discloses a pressure/differential pressure transmitter where a hydraulic path is filled with a fill fluid for transferring a pressure and a space is formed between a diaphragm and a wall surface on a main body side. The pressure/differential pressure transmitter includes the hydraulic path connected to the wall surface on the main body side and transfers a pressure received by the diaphragm to a sensor via the fill fluid filled in the space and hydraulic path, where a hydrogen occlusion material for occluding hydrogen atoms in the fill fluid is provided to at least a part of the fill fluid, wall surface on the main body side, and a section between the wall surface on the main body side and the sensor.